X-ray emissions from the supermassive black hole in the center of the Milky Way galazy, about 26,000 light years from Earth. Credit: NASA/CXC/APC/Université Paris Diderot/M.Clavel et al
How’s that for a beacon? NASA’s Chandra X-ray Observatory has tracked down evidence of at least a couple of past luminous outbursts near the Milky Way’s huge black hole. These flare-ups took place sometime in the past few hundred years, which is very recently in astronomical terms.
“The echoes from Sagittarius A were likely produced when large clumps of material, possibly from a disrupted star or planet, fell into the black hole,” the Chandra website stated.
“Some of the X-rays produced by these episodes then bounced off gas clouds about 30 to 100 light years away from the black hole, similar to how the sound from a person’s voice can bounce off canyon walls. Just as echoes of sound reverberate long after the original noise was created, so too do light echoes in space replay the original event.”
The astronomers saw evidence of “rapid variations” in how X-rays are emitted from gas clouds circling the hole, revealing clues that the area likely got a million times brighter at times.
This graphic depicts HD 189733b, the first exoplanet caught passing in front of its parent star in X-rays. Credit: X-ray: NASA/CXC/SAO/K.Poppenhaeger et al; Illustration: NASA/CXC/M.Weiss.
In the medical field, X-rays are used for finding and diagnosing all sorts of ailments hidden inside the body; in astronomy X-rays can also be used to study obscured objects like pulsars and black holes. Now, for the first time, X-rays have been used to study another object in space that tends to be difficult to spot: an extra solar planet. The Chandra X-ray Observatory and the XMM Newton Observatory combined their X-ray super powers to look at an exoplanet passing in front of its parent star.
This is not a new detection of an exoplanet – this same exoplanet, named HD 189733b has been one of the most-observed planets orbiting another star, and was recently in the news for Hubble confirming the planet’s ocean-blue atmosphere and the likelihood of having glass raining down on the planet.
But being able to see the exoplanet in X-rays is good news for future studies and perhaps even detections of planets around other stars.
“Thousands of planet candidates have been seen to transit in only optical light,” said Katja Poppenhaeger of Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., who led the new study, which will be published in the Aug. 10 edition of The Astrophysical Journal. “Finally being able to study one in X-rays is important because it reveals new information about the properties of an exoplanet.”
Artist’s impression of the deep blue planet HD 189733b, based on observations from the Hubble Space Telescope. Credit: NASA/ESA.
HD 189733b is a Jupiter-sized extrasolar planet orbiting a yellow dwarf star that is in a binary system called HD 189733 in the constellation of Vulpecula, near the Dumbell Nebula, approximately 62 light years from Earth.
This huge gas giant orbits very close to its host star and gets blasted with X-rays from its star — tens of thousands of times stronger than the Earth receives from the Sun — and endures wild temperature swings, reaching scorching temperatures of over 1,000 degrees Celsius. Astronomers say it likely rains glass (silicates) – sideways — in howling 7,000 kilometer-per-hour winds.
But it is relatively close to Earth, and so it has been oft-studied by many other space and ground-based telescopes.
In a blog post, Poppenhaeger said she was inspired by the launch of the Kepler telescope, and wondered if exoplanets could be seen in X-rays. She was excited when she found archived data from XMM Newton showing a fifteen hour long observation of the star HD 189733 and the “Hot Jupiter” HD 189733b was crossing in front of the star during that observation.
But the light curve was disappointing, she said. “The star is magnetically active, meaning that its corona is bright and flickering, so its X-ray light curve showed lots of scatter. Looking for a transit signal in this light curve was like trying to hear a whisper in a noisy pub,” Poppenhaeger wrote.
She knew with more data, the transit signal would be clearer, so she applied for – and got – time on Chandra to observe this exoplanet.
She combined the data from all the observations and was finally successful. “I could detect the transit of the planet in X-rays,” Poppenhaeger said. “What surprised me was how deep the transit was: The planet swallowed about 6-8% of the X-ray light from the star, while it only blocked 2.4% of the starlight at optical wavelengths. That means that the planet’s atmosphere blocks X-rays at altitudes of more than 60,000 km above its optical radius – a 75% larger radius in X-rays!”
That means that the outer atmosphere has to be heated up to about 20,000 K to sustain itself at such high altitudes. Additionally, the planet loses its atmosphere about 40% faster than thought before.
Poppenhaeger said she and her colleagues will test more X-ray observations of other similar planets such as CoRoT-2b to learn more about how stars can affect a planet’s atmosphere.
G1.9+0.3 in an image by the Chandra X-ray Observatory. Credit: X-ray (NASA/CXC/NCSU/K.Borkowski et al.); Optical (DSS)
In 2008, astronomers discovered a star relatively nearby Earth went kablooie some 28,000 light-years away from us. Sharp-eyed astronomers, as they will do, trained their telescopes on it to snap pictures and take observations. Now, fresh observations from the orbiting Chandra X-ray Observatory suggest that supernova was actually a double-barrelled explosion.
This composite picture of G1.9+0.3, coupled with models by astronomers, suggest that this star had a “delayed detonation,” NASA stated.
“First, nuclear reactions occur in a slowly expanding wavefront, producing iron and similar elements. The energy from these reactions causes the star to expand, changing its density and allowing a much faster-moving detonation front of nuclear reactions to occur.”
To explain a bit better what’s going on with this star, there are two main types of supernovas:
In a Type Ia supernova, a white dwarf (left) draws matter from a companion star until its mass hits a limit which leads to collapse and then explosion. Credit: NASA
– Type Ia: When a white dwarf merges with another white dwarf, or picks up matter from a close star companion. When enough mass accretes on the white dwarf, it reaches a critical density where carbon and oxygen fuse, then explodes.
– Type II: When a massive star reaches the end of its life, runs out of nuclear fuel and sees its iron core collapse.
NASA said this was a Type Ia supernova that “ejected stellar debris at high velocities, creating the supernova remnant that is seen today by Chandra and other telescopes.”
In this artist’s conception, a supernova explosion is about to obliterate an orbiting Saturn-like planet. Credit: David A. Aguilar (CfA)
You can actually see the different energies from the explosion in this picture, with red low-energy X-rays, green intermediate energies and blue high-energies.
“The Chandra data show that most of the X-ray emission is “synchrotron radiation,” produced by extremely energetic electrons accelerated in the rapidly expanding blast wave of the supernova. This emission gives information about the origin of cosmic rays — energetic particles that constantly strike the Earth’s atmosphere — but not much information about Type Ia supernovas,” NASA stated.
Also, unusually, this is an assymetrical explosion. There could have been variations in how it expanded, but astronomers are looking to map this out with future observations with Chandra and the National Science Foundation’s Karl G. Jansky Very Large Array.
Check out more information about this supernova in the scientific paper led by North Carolina State University.
A new analysis of data from the Chandra space telescope revealed 26 black hole candidates in the Andromeda Galaxy. This is the largest collection of possible black holes found in another galaxy besides that of the Milky Way, Earth's home galaxy. Credit: X-ray (NASA/CXC/SAO/R.Barnard, Z.Lee et al.), Optical (NOAO/AURA/NSF/REU Prog./B.Schoening, V.Harvey; Descubre Fndn./CAHA/OAUV/DSA/V.Peris)
More than two DOZEN potential black holes have been found in the nearest galaxy to our own. As if that find wasn’t enough, another research group is teaching us why extremely high-energy X-rays are present in black holes.
The Andromeda Galaxy (M31) is home to 26 newly found black hole candidates that were produced from the collapse of stars that are five to 10 times as massive as the sun.
Using 13 years of observations from NASA’s Chandra X-Ray Observatory, a research team pinpointed the locations. They also corroborated the information with X-ray spectra (distribution of X-rays with energy) from the European Space Agency’s XMM-Newton X-ray observatory.
“When it comes to finding black holes in the central region of a galaxy, it is indeed the case where bigger is better,” stated co-author Stephen Murray, an astronomer at Johns Hopkins University and the Harvard-Smithsonian Center for Astrophysics.
A close-up of the candidate black holes in Andromeda, as seen by the Chandra X-Ray Observatory. Credit: X-ray (NASA/CXC/SAO/R.Barnard, Z.Lee et al.), Optical (NOAO/AURA/NSF/REU Prog./B.Schoening, V.Harvey; Descubre Fndn./CAHA/OAUV/DSA/V.Peris
“In the case of Andromeda, we have a bigger bulge and a bigger supermassive black hole than in the Milky Way, so we expect more smaller black holes are made there as well,” Murray added.
The total number of candidates in M31 now stands at 35, since the researchers previously identified nine black holes in the area. All told, it’s the largest number of black hole candidates identified outside of the Milky Way.
Meanwhile, a study led by the NASA Goddard Space Flight Center examined the high-radiation environment inside a black hole — by simulation, of course. The researchers performed a supercomputer modelling of gas moving into a black hole, and found that their work helps explain some mysterious X-ray observations of recent decades.
Researchers distinguish between “soft” and “hard” X-rays, or those X-rays that have low and high energy. Both types have been observed around black holes, but the hard ones puzzled astronomers a bit.
Here’s what happens inside a black hole, as best as we can figure:
– Gas falls towards the singularity, orbits the black hole, and gradually becomes a flattened disk;
– As gas piles up in the center of the disk, it compresses and heats up;
– At a temperature of about 20 million degrees Fahrenheit (12 million degrees Celsius), the gas emits “soft” X-rays.
So where did the hard X-rays — that with energy tens or even hundreds of times greater than soft X-rays — come from? The new study showed that magnetic fields are amplified in this environment that then “exerts additional influence” on the gas, NASA stated.
Artist’s conception of the Chandra X-Ray Observatory. Credit: NASA
“The result is a turbulent froth orbiting the black hole at speeds approaching the speed of light. The calculations simultaneously tracked the fluid, electrical and magnetic properties of the gas while also taking into account Einstein’s theory of relativity,” NASA stated.
One key limitation of the study was it modelled a non-rotating black hole. Future work aims to model one that is rotating, NASA added.
You can check out more information about these two studies below:
This all-sky Fermi view includes only sources with energies greater than 10 GeV. From some of these sources, Fermi's LAT detects only one gamma-ray photon every four months. Brighter colors indicate brighter gamma-ray sources. Credit: NASA/DOE/Fermi LAT Collaboration
The universe, most cosmologists tell us, began with a bang. At some point, the lights turned on. How much light has the universe produced since it was born, 13.8 billion years ago?
It seems a difficult answer at first glance. Turn on a light bulb, turn it off and the photons appear to vanish. In space, however, we can track them down. Every light particle ever radiated by galaxies and stars is still travelling, which is why we can peer so far back in time with our telescopes.
A new paper in the Astrophysical Journal explores the nature of this extragalactic background light, or EBL. Measuring the EBL, the team states, “is as fundamental to cosmology as measuring the heat radiation left over from the Big Bang (the cosmic microwave background) at radio wavelengths.”
Turns out that several NASA spacecraft have helped us understand the answer. They peered at the universe in every wavelength of light, ranging from long radio waves to short, energy-filled gamma rays. While their work doesn’t go back to the origin of the universe, it does give good measurements for the last five billion years or so. (About the age of the solar system, coincidentally.)
Artist’s conception of how gamma rays (dashed lines) bump against photons of electromagnetic background light, producing electrons and positrons. Credit: Nina McCurdy and Joel R. Primack/UC-HiPACC; Blazar: Frame from a conceptual animation of 3C 120 created by Wolfgang Steffen/UNAM
It’s hard to see this faint background light against the powerful glow of stars and galaxies today, about as hard as it is to see the Milky Way from downtown Manhattan, the astronomers said.
The solution involves gamma rays and blazars, which are huge black holes in the heart of a galaxy that produce jets of material that point towards Earth. Just like a flashlight.
These blazars emit gamma rays, but not all of them reach Earth. Some, astronomers said, “strike a hapless EBL photon along the way.”
When this happens, the gamma ray and photon each zap out and produce a negatively charged electron and a positively charged positron.
More interestingly, blazars produce gamma rays at slightly different energies, which are in turn stopped by EBL photons at different energies themselves.
So, by figuring out how many gamma rays with different energies are stopped by the photons, we can see how many EBL photons are between us and the distant blazars.
Scientists have now just announced they could see how the EBL changed over time. Peering further back in the universe, as we said earlier, serves as a sort of time machine. So, the further back we see the gamma rays zap out, the better we can map out the EBL’s changes in earlier eras.
The Fermi Gamma-ray Space Telescope (formerly called GLAST). Credit: NASA
To get technical, this is how the astronomers did it:
– Compared the gamma-ray findings of the Fermi Gamma-ray Space Telescope to the intensity of X-rays measured by several X-ray observatories, including the Chandra X-Ray Observatory, the Swift Gamma-Ray Burst Mission, the Rossi X-ray Timing Explorer, and XMM/Newton. This let astronomers figure out what the blazars’ brightnesses were at different energies.
– Comparing those measurements to those taken by special telscopes on the ground that can look at the actual “gamma-ray flux” Earth receives from those blazars. (Gamma rays are annihilated in our atmosphere and produce a shower of subatomic particles, sort of like a “sonic boom”, called Cherenkov radiation.)
The measurements we have in this paper are about as far back as we can see right now, the astronomers added.
“Five billion years ago is the maximum distance we are able to probe with our current technology,” stated the paper’s lead author, Alberto Dominguez.
“Sure, there are blazars farther away, but we are not able to detect them because the high-energy gamma rays they are emitting are too attenuated by EBL when they get to us—so weakened that our instruments are not sensitive enough to detect them.”
The Vela pulsar, a neutron star that was formed when a massive star collapsed. Credit: NASA
This incredible new movie of the Vela pulsar has the unnerving appearance of the Phantom of the Opera – wearing not only a mask, but also a steam-blowing hat like the Tin Man in “The Wizard of Oz.” What you are seeing here are observations from the Chandra X-ray Observatory, showing a fast moving jet of particles produced by a rapidly rotating neutron star. Scientists say these observations may provide new insight into the nature of some of the densest matter in the universe.
The Vela pulsar is about 1,000 light-years from Earth, about 19 km (12 miles) in diameter, and makes a complete rotation in 89 milliseconds. As the pulsar whips around, it spews out a jet of charged particles that race along the pulsar’s rotation axis at about 70 percent of the speed of light. The Chandra data used in the movie were obtained from June to September 2010, and it may suggest the pulsar may be slowly wobbling, or precessing, as it spins. The period of the precession, which is analogous to the slow wobble of a spinning top, is estimated to be about 120 days.
“We think the Vela pulsar is like a rotating garden sprinkler — except with the water blasting out at over half the speed of light,” said Martin Durant of the University of Toronto in Canada, who is the first author of the paper describing these results.
The eight images shown in the movie suggest that the pulsar may be slowly wobbling, or precessing, as it spins. If the evidence for precession of the Vela pulsar is confirmed, it would be the first time that a jet from a neutron star has been found to be wobbling, or precessing, in this way.
One possible cause of precession for a spinning neutron star is that it has become slightly distorted and is no longer a perfect sphere. This distortion might be caused by the combined action of the fast rotation and “glitches”, sudden increases of the pulsar’s rotational speed due to the interaction of the superfluid core of the neutron star with its crust.
This is the second Chandra movie of the Vela pulsar. The first one, released in 2003, looks like a Halloween Jack-o-lanatern gone wrong:
This movie contains shorter, unevenly spaced observations so that the changes in the jet were less pronounced and the authors did not argue that precession was occurring. However, based on the same data, Avinash Deshpande of Arecibo Observatory in Puerto Rico and the Raman Research Institute in Bangalore, India, and the late Venkatraman Radhakrishnan, argued in a 2007 paper that the Vela pulsar might be precessing.
The Earth also precesses as it spins, with a period of about 26,000 years. In the future Polaris will no longer be the “north star” and other stars will take its place. The period of the Vela precession is much shorter and is estimated to be about 120 days.
Wide field Optical and X-ray image of the supernova remnant in the Vela Pulsar region. Credit: Anglo-Australian Observatory.
The supernova that formed the Vela pulsar exploded over 10,000 years ago. This optical image from the Anglo-Australian Observatory’s UK Schmidt telescope shows the enormous apparent size of the supernova remnant formed by the explosion. The full size of the remnant is about eight degrees across, or about 16 times the angular size of the Moon. The square near the center shows the Chandra image with a larger field-of-view than used for the movie, with the Vela pulsar in the middle.
NGC 3627 glows in the combined light of Hubble, Chandra, Spitzer and the Very Large Telescope in this image. Astronomers conducted a survey of 62 galaxies, including NGC 3627 to study monster black holes at their centers.
It’s not just pretty, it’s science. Like a starry watercolor, astronomers combining light from Earth and space-based observatories found 37 new supermassive black hole candidates lurking in nearby galaxies.
Included in that survey is NGC 3627 pictured above. Astronomers combined X-ray data from NASA’s Chandra X-ray Observatory, infrared data from the Spitzer Space Telescope, and optical data from the Hubble Space Telescope and the Very Large Telescope. The other images give the galaxy context but it’s the ghostly blue images from Chandra that show super bright in the X-ray images; X-ray light powered by material falling into a monster black hole.
Gas and dust slowly spins around the black hole creating a flattened disk, or accretion disk. As material falls inward, it heats up and releases large amounts of energy that shine brightly in the ultraviolet region of the spectrum.
NGC 3627, located about 30 million light-years from Earth, was just one of a survey of 62 nearby galaxies using archived data from Chandra and data from the Spitzer Infrared Nearby Galaxy Survey. Of those, 37 galaxies contained bright X-ray sources, indicating active black holes at their cores. Scientists believe that seven of those sources are new supermassive black hole candidates.
Combining ultraviolet and infrared observations confirm previous Chandra results that found that there may be many more galaxies powered by monster black holes than believed previously through optical surveys. Scientists say in the paper that low-levels of black hole activity previously may have been hidden by dust or washed out by the bright light of the galaxy.
Image caption: Bright X-ray sources glow a ghostly blue in this image in NGC 3627 from NASA’s Chandra X-ray Observatory. A study confirms previous Chandra results that indicate that more galaxies powered by monster black holes populate the cosmos.
Image credit: X-ray: NASA/CXC/U.Mich./S.Oey, IR: NASA/JPL, Optical: ESO/WFI/2.2-m. Zoom by John Williams/TerraZoom using Zoomify
When NASA combines images from different telescopes, they create dazzling scenes of celestial wonder and in the process we learn a few more things. Behold this wonder of combined light, known as LHA 120-N 44, or N 44 for short. Zoom into the scene using the toolbar at the bottom of the image. Click the farthest button on the right of the toolbar to see this wonder in full-screen. (Hint: press the “Esc” key to get back to work)
A composite image of Chandra X-ray data shows a rainbow of reds, yellows, green, blue and purple, from lower to higher energies. Optical data from the Digitized Sky Survey, shown in pale yellow and blue, offer a starry background for the image. Optical: DSS
An arc of hot gas that spewed from the Kepler Supernova offers tantalizing clues that the cataclysmic stellar explosion of 1604 was not only more powerful than previously thought but also farther away according to a recent study using Chandra X-ray Observatory data published in the September 1, 2012 edition of The Astrophysical Journal.
A new star appeared in the autumn skies of 1604. Although it was described by other astronomers, it was famous astronomer Johannes Kepler who thoroughly detailed the the second supernova sighting in a generation. The star shined more brilliant than Jupiter and remained visible – even during the day – over several weeks.
Look for Kepler’s Supernova at the foot of the constellation Ophiuchus, the Serpent Bearer, in visible light and you won’t see much. But the hot gas and dust glow brightly in the X-ray images from Chandra. Astronomers have long puzzled over Kepler’s Supernova. Astronomers now know the explosion that created the remnant was a Type Ia supernova. Supernovae of this class occur when a white dwarf, the white-hot dead core of a once Sun-like star, gains mass by either merging with another white dwarf or drawing gas onto its surface from a larger companion star until temperatures soar and thermonuclear processes spiral out of control resulting in a detonation that destroys the star.
Kepler’s Supernova is a bit different because the expanding debris cloud is shaped by gas and dust clouds throughout the area. Most Type Ia supernovae are symmetrical; nearly perfect expanding bubbles of material. A quick look at the Chandra image of the supernova and one notices the bright arc of material across the top edge of shockwave. In one model, a pre-supernova white dwarf and its companion were moving through a nebulous area creating a bow shock, like a boat plowing through water, in front. Another model suggests that the glowing arc is the edge of the supernova shockwave as it passes through an area of increasingly dense gas and dust. Both models push the distance of the supernova from the previously believed 13,000 light-years to more than 20,000 light-years from Earth, scientists say in the paper.
Scientists also found large amounts of iron by looking at the X-ray light from Chandra meaning that the explosion was far more powerful than an average Type Ia supernova. Astronomers have observed a similar Type Ia supernova using Chandra and an optical telescope in the Large Magellanic Cloud.
Kepler’s Supernova is the last Milky Way supernova visible to the naked eye. It was the second supernova to be observed in that generation after SN 1572 in Cassiopeia studied by the famous astronomer Tycho Brahe.
About the author: John Williams is owner of TerraZoom, a Colorado-based web development shop specializing in web mapping and online image zooms. He also writes the award-winning blog, StarryCritters, an interactive site devoted to looking at images from NASA’s Great Observatories and other sources in a different way. A former contributing editor for Final Frontier, his work has appeared in the Planetary Society Blog, Air & Space Smithsonian, Astronomy, Earth, MX Developer’s Journal, The Kansas City Star and many other newspapers and magazines. Follow John on Twitter @terrazoom.
Before and After Images in X-ray and Optical Light In Chandra observations that spanned several years, the ULX in M83 increased in X-ray brightness by at least 3,000 times. This sudden brightening is one of the largest changes in X-rays ever seen for this type of object, which do not usually show dormant periods. (Credit: Optical: ESO/VLT; Close-up - X-ray: NASA/CXC/Curtin University/R.Soria et al., Optical: NASA/STScI/Middlebury College/F.Winkler et al.)
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Astronomers keeping an eye out for a supernova explosion in the nearby galaxy M83 instead witnessed a prodigious blast of another type: a new ultraluminous X-ray source, or ULX. In what scientists are calling an “extraordinary outburst,” the ULX in M83 increased in X-ray brightness by at least 3,000 times, one of the largest changes in X-rays ever seen for this type of object.
“The flaring up of this ULX took us by surprise and was a sure sign we had discovered something new about the way black holes grow,” said Roberto Soria of Curtin University in Australia, who led the new study.
The researchers say this blast provides direct evidence for a population of old, volatile stellar black holes and gives new insight into the nature of a mysterious class of black holes that can produce as much energy in X-rays as a million suns radiate at all wavelengths.
Astrophysicist Bill Blair of Johns Hopkins University, writing in the Chandra Blog, “A Funny Thing Happened While Waiting for the Next Supernova in M83,” said this galaxy, also known as the Southern Pinwheel Galaxy, “is an amazing gift of nature. At 15 million light years away, it is actually one of the closer galaxies (only 7-8 times more distant than the Andromeda galaxy), but it appears as almost exactly face-on, giving earthlings a fantastic view of its beautiful spiral arms and active star-forming nucleus.”
M83 has generated six observed supernovas since 1923, but the last one seen was in 1983. “We are overdue for a new supernova!” Blair wrote.
So, many astronomers have been observing M83, hoping to spot a new supernova, but instead saw a dramatic jump in X-ray brightness, which according to the researchers, likely occurred because of a sudden increase in the amount of material falling into the black hole.
A ULX can give off more X-rays than most “normal” binary systems in which a companion star is in orbit around a neutron star or black hole. The super-sized X-ray emission suggests ULXs contain black holes that might be much more massive than the ones found elsewhere in our galaxy.
Composite image of spiral galaxy M83. (X-ray: NASA/CXC/Curtin University/R. Soria et al., Optical: NASA/STScI/ Middlebury College/F. Winkler et al.)
The companion stars to ULXs, when identified, are usually young, massive stars, implying their black holes are also young. The latest research, however, provides direct evidence that ULXs can contain much older black holes and some sources may have been misidentified as young ones.
The observations of M83 were made over a several year period with Chandra. No sign of the ULX was found in historical X-ray images made with Einstein Observatory in 1980, ROSAT in 1994, the European Space Agency’s XMM-Newton in 2003 and 2008, NASA’s Swift observatory in 2005, the Magellan Telescope observations in April 2009 or in a Hubble image obtained in August 2009.
But in 2011, Soria and his colleagues used optical images from the Gemini Observatory and NASA’s Hubble Space Telescope and saw a bright blue source at the position of the X-ray source.
The lack of a blue source in the earlier images indicates the black hole’s companion star is fainter, redder and has a much lower mass than most of the companions that previously have been directly linked to ULXs. The bright, blue optical emission seen in 2011 must have been caused by a dramatic accumulation of more material from the companion star.
“If the ULX only had been observed during its peak of X-ray emission in 2010, the system easily could have been mistaken for a black hole with a massive, much younger stellar companion, about 10 to 20 million years old,” said co-author Blair.
The companion to the black hole in M83 is likely a red giant star at least 500 million years old, with a mass less than four times the sun’s. Theoretical models for the evolution of stars suggest the black hole should be almost as old as its companion.
Another ULX containing a volatile, old black hole recently was discovered in the Andromeda galaxy by a team led by Amanpreet Kaur from Clemson University, published in the February 2012 issue of Astronomy and Astrophysics. Matthew Middleton and colleagues from the University of Durham reported more information in the March 2012 issue of the Monthly Notices of the Royal Astronomical Society. They used data from Chandra, XMM-Newton and HST to show the ULX is highly variable and its companion is an old, red star.
“With these two objects, it’s becoming clear there are two classes of ULX, one containing young, persistently growing black holes and the other containing old black holes that grow erratically,” said Kip Kuntz, a co-author of the new M83 paper, also of Johns Hopkins University. “We were very fortunate to observe the M83 object at just the right time to make the before and after comparison.”
A paper describing these results will appear in the May 10th issue of The Astrophysical Journal.
